Officials do not yet know what caused the sinkhole to form...but are working on it

As it widened, a parked dark van and a street lamp tumbled into the sinkhole.

Tom Herlihy was walking along Rideau Street when he heard and smelt the gas leak: "A high-pressure natural gas line escaping is very distinct, it's a high-pressure whistle.

"You could smell it in the area immediately, and people were running away from it, you could tell something was amiss."

On getting a better look from an upper storey of a nearby hotel, Herlihy told CBC: "I caught the hole expanding and the car falling in and the gas just roiling the water, causing the dirt underneath the street to erode and collapse. And it's really deep."

Charing Cross closure

Speculation was rife that the cavernous hole in the pavement was linked to a 1½-mile (2.5km) underground tunnel being dug for the city’s light rail transit system. Workers had been excavating in the area when the sinkhole began to form. All of them had made it out safely.

But Watson said it was too early to say whether the sinkhole was related to the underground drilling. “We can’t confirm whether the tunnel had any impact on the sinkhole or whether it was a water main break or whether it was a leak of some type that destabilised the soil.”

City officials would, he hoped, be able to pinpoint the exact cause in the coming days.

Nobody was hurt or reported missing.

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